Effect Of Nitriding Temperature Research Articles

SBA‐15‐Oxynitrides as a Solid‐Base Catalyst: Effect of Nitridation Temperature on Catalytic Activity

AbstractSolid bases, such as SBA‐15‐oxynitrides, have attracted considerable interest for potential applications as catalysts in important industrial processes. Reported herein is that by simply tuning the temperature of nitridation (ammonolysis), the catalytic activity of these solid bases can be enhanced. Solid‐state NMR spectroscopy and XPS studies provided the reasoning behind this change in activity.

SBA-15-Oxynitrides as a Solid-Base Catalyst: Effect of Nitridation Temperature on Catalytic Activity.

Solid bases, such as SBA-15-oxynitrides, have attracted considerable interest for potential applications as catalysts in important industrial processes. Reported herein is that by simply tuning the temperature of nitridation (ammonolysis), the catalytic activity of these solid bases can be enhanced. Solid-state NMR spectroscopy and XPS studies provided the reasoning behind this change in activity.

Effects of Nitridation Temperature on Characteristics of Gallium Nitride Thin Films Prepared Via Two-Step Method

In this research, the growth of GaN thin films on c-plane sapphire (0001) substrates via two-step method without the assist of buffer layer and catalysts was demonstrated. First, gallium oxide (Ga2O3) thin films were deposited on sapphire substrates by radio frequency magnetron sputtering method. The deposited Ga2O3 thin films were then nitridated at various temperatures. In this research, attention is focused on the influence of nitridation temperatures on the structural and optical properties of the synthesized GaN thin films. It is revealed that 950 °C is the optimal nitridation temperature for synthesizing hexagonal wurtzite GaN thin film with preferential (0002) growth direction.

Orientation dependence of nitrogen supersaturation in austenitic stainless steel during low-temperature gas-phase nitriding

A hardened surface layer was produced on 316L austenitic stainless steel via low-temperature gas-phase nitriding. The effects of nitriding temperature, nitrogen activity and processing time were systematically studied. Concentration–depth profiling by Auger electron spectroscopy revealed very high levels (up to 25at.%) of interstitial nitrogen in solid solution. This causes a lattice parameter expansion of up to 10% at the alloy surface. X-ray diffractometry revealed that the expansion – and thus the level of nitrogen supersaturation – strongly depends on the crystallographic orientation. We attribute this effect to the elastic anisotropy of austenite, exacerbated by a nitrogen-induced paramagnetic-to-ferromagnetic transition.

The effect of nitridation temperature on the structural, optical and electrical properties of GaN nanoparticles

Nitridation at high temperature enhances the crystalline and optical quality of GaN nanoparticles synthesized by a novel chemical co-precipitation method.

Nitridation Temperature Effects on Electronic and Chemical Properties of (Ga1–xZnx)(N1–xOx) Solid Solution Nanocrystals

Solid solution nanocrystals of gallium nitride–zinc oxide have been realized as potential photocatalysts for visible light driven overall water splitting. The band gap of these materials has been found to narrow further into the visible region as a function of increasing zinc oxide concentration, and thus, it is desirable to synthesize zinc oxide-rich gallium nitride–zinc oxide solid solutions. In this paper, we discuss the effects of using nitridation temperature to control zinc oxide content on the electronic and chemical properties of gallium nitride–zinc oxide solid solution nanostructures. The effect of nitridation temperature was studied using X-ray absorption fine structure (XAFS), including both X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), and X-ray excited optical luminescence (XEOL). It was determined that using nitridation temperature as a method of controlling zinc oxide concentration results in solid solutions with poor crystallinity, phas...

Kinetic study on the direct nitridation of silicon powders diluted with α-Si3N4 at normal pressure

Silicon nitride (Si3N4) powders were prepared by the direct nitridation of silicon powders diluted with α-Si3N4 at normal pressure. Silicon powders of 2.2 μm in average diameter were used as the raw materials. The nitriding temperature was from 1623 to 1823 K, and the reaction time ranged from 0 to 20 min. The phase compositions and morphologies of the products were analyzed by X-ray diffraction and scanning electron microscopy, respectively. The effects of nitriding temperature and reaction time on the conversion rate of silicon were determined. Based on the shrinking core model as well as the relationship between the conversion rate of silicon and the reaction time at different temperatures, a simple model was derived to describe the reaction between silicon and nitrogen. The model revealed an asymptotic exponential trend of the silicon conversion rate with time. Three kinetic parameters of silicon nitridation at atmospheric pressure were calculated, including the pre-exponential factor (2.27 cm·s−1) in the Arrhenius equation, activation energy (114 kJ·mol−1), and effective diffusion coefficient (6.2×10−8 cm2·s−1). A formula was also derived to calculate the reaction rate constant.

The effect of nitriding temperature on hardness and microstructure of die steel pre-treated by ultrasonic cold forging technology

To promote the formation and growth of nitride layer, a befitting surface nano-crystallization process was introduced as a pre-treatment of nitriding, and an optimized nitriding temperature was investigated. A modification layer with a depth of 350μm was formed by ultrasonic cold forging technology (UCFT) on AISI D2 surface. A series of plasma nitriding experiments for both treated and untreated samples were conducted at various temperatures ranging from 350°C to 550°C for 4h. The influences of nitriding temperature on the hardness, microstructure, morphology and composition of the sample surface were investigated by micro-hardness tester, optical microscope (OM), 3D profile-meter and scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The diffusion of nitrogen and the formation of nitrides were markedly improved by UCFT pre-treatment. A thicker and harder nitrided layer was formed at a high nitriding temperature. However, as the nitriding temperature increased to 550°C, a stronger sputter occurred on the sample surface. The results presents that it is an optimized process to be pre-treated by UCFT and nitriding at 520°C for 4h.

Preparation of Ca-α-Sialon-SiC Multiphase Ceramics from Gasification Slag

The chemical composition, phase constituents and microstructure of gasification slag from Texaco gasifier, the carbothermal reduction nitridation of gasification slag were investigated by X-ray fluorescence spectrometry, X-ray diffractometry and scanning electron microscopy. The effect of nitridation temperature on the phase composition and morphology of nitridation reaction products was studied. Ca-α-sialon—SiC multiphase ceramics were fabricated and characterized. The results showed that: The coal gasification slag was an ideal raw material to synthesize Sialon powder. When introducing 3wt%Y2O3+2wt% MgO into sialon powder carbothermally synthesized at 1450°C, the Vickers hardness and fracture toughness of Sialon-SiC multiphase ceramics hot-pressed at 1650 °C were 18.6 GPa and 5.2 MPa·m1/2, respectively.

Ion Nitriding of CoCrMo Alloys

Medical grade cast CoCrMo alloy (F75) was ion nitrided under different process parameters including time (2, 9 hr) and temperature (600, 800 0C) at a gas mixture of 80%N2–20%H2. The nitrided surfaces were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). MicroVickers hardness tests were done on the cross sections of the nitrided specimens to investigate the hardness profile. The significant effects of nitriding temperature and time on the microstructure and hardness value of nitrided surface layers were displayed.

β-Ga2O3 单晶NH3中氮化的研究

Nitridated beta-Ga2O3 (100) substrate was investigated as the substrate for GaN epitaxial growth. The effects of nitridation temperature and surface roughness of beta-Ga2O3 wafers on the formation of GaN were studied. It was found that the most optimized nitridation temperature was 900 centigrade, and hexagonal GaN with preferred orientation was produced on the well-polished wafer. The nitridation mechanism was also discussed.

Preparation of Ultrafine β-Sialon Powder by Citrate Sol-Gel and Carbothermal Reduction Nitridation

Ultrafine β-sialon powder is synthesized by citrate sol-gel and carbothermal reduction and nitridation (CRN) process. The presence of small amounts of β-sialon as crystal seed can obviously accelerate the formation of final β-sialon product and lower its formation temperature. The effects of nitriding temperature on the formation of the final β-sialon are investigated. The mean particle size of the prepared β-sialon powder is 100 ~ 150 nm. The β-sialon precursor gel and the ultrafine β-sialon powder are characterized by XRD, TG-DTA and SEM. The isoelectric point of ultrafine β-sialon is pH 2.46.

QPQ Salt Bath Nitriding and Corrosion Resistance

The QPQ complex salt bath treatment is a type of surface strengthening technology which contains mainly salt bath nitriding and salt bath post-oxidizing processes. The effect of nitriding temperature and duration on the corrosion resistance of QPQ treated specimens is explored by immersion tests and salt spray tests in this paper. The material used in this study was 1020 annealed steel. In the immersion tests, the specimens were immersed in 3‰H2O2 and 10% NaCl water solution. In the salt spray tests, specimens were salt spray tested using a 5% NaCl neutral solution. The data indicate that, when the nitriding duration is less than 2 hours at temperature below 590(phase change will exist when the nitriding temperature is above 590 according to Fe-N phase diagram) , the higher temperature of the salt bath nitriding , the specimens will have the higher corrosion resistance. In addition we have found that nitriding for too short a time generates a thin compound layer, and nitriding for too long generates too much porosity. Both will deteriorate the corrosion resistance.

Synthesis of Nanocrystalline Zirconium Nitride Powders by Reduction–Nitridation of Zirconium Oxide

Nanocrystalline ZrN powder was synthesized by reduction–nitridation of nanosized ZrO2 powder in ammonia gas with magnesium as the reducing agent. The effects of nitridation temperature, holding time, and Mg:ZrO2 mole ratio on the powder properties were investigated. Cubic phase ZrN powder with a 30–100‐nm particle size was synthesized at 1000°C for 6 h, under a Mg:ZrO2 mole ratio of 10:1.

Tribological behaviour of plasma nitrided Ti-5Al-2Nb-1Ta alloy against UHMWPE

A detailed study has been made on the wear behaviour of untreated and plasma nitrided Ti-5Al-2Nb-1Ta orthopaedic alloy against ultra high molecular weight polyethylene (UHMWPE) using pin on disc tribometer under lubricated conditions. The effects of nitriding temperature and nitriding time on the basis of the evolution of the wear volume loss and friction coefficient were investigated. The wear resistance of the plasma nitrided alloys increased considerably when compared to the untreated alloy. The wear debris identified using X-ray diffraction measurements indicated the formation of titanium oxide and titanium oxynitride particles. The wear rate was found to increase with increase in load and sliding velocity.

Synthesis and characterization of TiO xN y assembled in oxynitrided mesoporous silica MCM-41

Titanium oxynitride (TiO x N y ) with varying nitrogen contents assembled in the pores of mesoporous material has been achieved by nitriding titania-modified MCM-41 under flowing NH 3 atmosphere. XRD, XPS, N 2 adsorption–desorption isotherms and UV-Vis spectra are employed to characterize the structure of the composite materials. The results show that titanium oxynitride is formed and crystallized at 700 °C when the nitridation time is 3 h. The MCM-41 host is also nitrided inevitably, while the mesostructure is still preserved. The effects of nitridation temperature on the formation of titanium oxynitride and structure of MCM-41 are systematically discussed.

Tribological performance of plasma nitrided gamma based titanium aluminides

Ti–48Al–2Nb–2Mn (at.%) alloy was plasma nitrided to investigate the effect of this thermochemical surface modification on the tribological behaviour of gamma based titanium aluminides. The effects of nitriding temperature, nitriding time and H 2/N 2 gas ratio were investigated. Characterisation of the microstructure and phases formed within the nitrided surface layers was performed using optical and electron microscopy, X-ray diffraction (XRD) and glow discharge spectroscopy (GDS). The wear resistance of the plasma nitrided samples increased considerably against ball bearing steel (AISI 52100). Experimental results indicated that time controls the thickness and nitriding temperature, and H 2/N 2 ratio is responsible for the crystal structure of the nitrided layers. The nitrided compound layers consist of TiN and Ti 2AlN phases. The diffusion zone, in most cases comprises of recrystallised gamma grains beneath the compound layer.

The impact of the nitridation process on the properties of the Si–SiO 2 interface

A newly developed technique for the simultaneous measurement of the oxide–silicon interface properties and of minority carrier lifetime in the silicon volume was used for a systematic study of the nitridation process of oxide films.This technique is based on the surface recombination velocity measurements, and does not require the formation of a capacitor structure, so it is suitable for the measurement of as-grown interface properties. Oxides grown both in dry and in wet environments were prepared, and nitridation processes in N 2O and in NO were compared to N 2 annealing processes. The effect of nitridation temperature and duration were also studied, and processes of rapid thermal oxidation (RTO) and nitridation (RTN) were compared to conventional furnace nitridation processes. Surface recombination velocity was correlated with nitrogen concentration at the oxide–silicon interface obtained by secondary ion mass spectroscopy (SIMS) measurements. Surface recombination velocity (hence surface state density) decreases with increasing nitrogen pile-up at the oxide–silicon interface, indicating that in nitrided interfaces surface state density is limited by nitridation. NO treatments are much more effective than N 2O treatments in the formation of a nitrogen–rich interface layer and, as a consequence, in interface state reduction. X-ray photoelectron spectrometry (XPS) analyses were used to extend our correlation to very thin oxides (3 nm).

Characterization of nitrided silicon-silicon dioxide interfaces

ABSTRACTA newly-developed technique for the simultaneos characterization of the oxide-silicon interface properties and of bulk impurities was used for a systematic study of the nitridation process of thin oxides. This technique is based upon surface recombination velocity measurements, and does not require the formation of a capacitor structure, so it is very suitable for the characterization of as-grown interfaces.Oxides grown both in dry and in wet enviroments were considered, and nitridation processes in N2O and in NO were compared to N2 annealing processes. The effect of nitridation temperature and duration were also studied, and RTO/RTN processes were compared to conventional furnace nitridation processes.Surface recombination velocity was correlated with nitrogen concentration at the oxide-silicon interface obtained by Secondary Ion Mass Spectroscopy (SIMS) measurements. Surface recombination velocity (hence surface state density) decreases with increasing nitrogen pile-up at the oxide-silicon interface, indicating that in nitrided interfaces surface state density is limited by nitridation. NO treatments are much more effective than N2O treatments in the formation of a nitrogen-rich interface layer and, as a consequence, in surface state reduction.Surface state density was measured in fully processed wafers before and after constant current stress. After a complete device process surface states are annealed out by hydrogen passivation, however they are reactivated by the electrical stress, and surface state results after stress were compared with data of surface recombination velocity in as-processed wafers.

Surface Characterization of GaN Formation on GaAs(100) Using Ammonia

AbstractThe GaN formation on GaAs(100) using NH3 has been investigated using synchrotron radiation photoemission spectroscopy and an atomic force microscope (AFM). This study showed the effect of nitridation temperature on the compositional change, the chemical states, and the surface morphological changes in the nitridated surface layer. It was observed that ammonia is decomposed to an activated nitrogen atom above 700°C forming GaN on the surface. A thermally nitridated layer was composed of metallic Ga and GaN islands elongated along the [011] direction to relax the tensile strain in the [011] direction. As the nitridation temperature increased, the composition of GaN increased in the nitridated layer due to the efficient thermal decomposition of NH3 and the subsequent incorporation of the N atom to the metallic Ga. The surface morphology of the nitridated layer was also sensitive to the nitridation temperature and a smooth surface morphology could be obtained on the surface nitridated at 700°C.